578 THE INSCRIPTIONS AT COPAN. 
From all the evidence now available it appears probable that the Maya 
chronological system was devised some time before 8.6.2.4.17, although not neces- 
sarily long prior thereto, to keep account of periods longer than the Calendar 
Round, i. ¢., 52 years of 365 days each. For this purpose a remarkable vigesimal 
mathematical system, including numeration by position, a fixed hypothetical 
starting-point, and an ingenious arithmetical notation of bars and dots and several 
specialized characters for zero, was invented, but underlying this, and of a still 
earlier date, there were (1) a sacred or divinitory year composed of 20 names com- 
bined with 13 numerals, making 260 days, and (2) a solar year fixed at 365 days 
in length, i.¢., composed of 18 months of 20 days each and a closing period of 5 days, 
as the two basic elements of Maya chronology. 
At first this extraordinarily accurate chronology was utilized for the record of 
any date, regardless of when it occurred, as evidenced by the casuality of the 
earliest dates, 8.6.2.4.17, 8.14.3.1.12, 8.14.10.13.15, and possibly 8.15.10.3.12, but 
very early, perhaps within a century of the last one of these, 7. ¢., about the begin- 
ning of Cycle 9, an exceedingly important change was introduced, no less than the 
practice of restricting the erection, of the larger monuments at least, to the ends of 
even periods in their chronological era. 
Several fairly obvious factors must have contributed largely to the origin and 
development of this practice. In the first place, to erect a monument or dedicate 
a smaller object after the event which it was to commemorate, was to violate the 
whole Mayan conception of time. The Maya conceived, measured, and recorded 
time in terms of elapsed units, which kept them continually looking forward into 
the future for their dates of ceremonial importance, 1. ¢., those which would close 
their time-periods. This of itself would tend to restrict the erection and dedica- 
tion of monuments to dates determined in advance by the passage of successive 
units of their chronological system, rather than to encourage the memorialization 
of early events at fortuitously chosen later times. 
Another very practical advantage to which this custom gave rise was the ample 
opportunity it afforded the priests to make the necessary arrangements for these 
important occasions, which the writer has pointed out in Chapter V required 
considerable forethought, elaborate planning, and coordination of activities in the 
not inconsiderable mechanical labor involved in quarrying, transporting, and 
erecting the monuments, to say nothing of the artistic efforts involved in their 
sculpture. 
A third factor was that of economic necessity. The work of many kinds, 
required to bring a monument to the point of completion must have withdrawn 
from purely economic production many laborers at not infrequent intervals, and 
as the period-endings in a very brief time shift all around the cycle of the seasonal 
year, it is obvious that careful planning was necessary to prevent these religio- 
esthetic activities from interfering with the more urgent need of producing corn and 
cotton, 1. ¢., food and clothing, in sufficient quantities to meet the requirements of 
the community. The latter demands were imperative. The beginning of the dry 
season fixed the time when the bush had to be felled, the beginning of the rainy 
season when the fields had to be planted. These labors brooked no delay, and other 
activities, religious, architectural, etc., had to be made to conform to the exigencies 
of agriculture. Thus the selection, a long time in advance, 5, 10, and 20 years, of 
the dates upon which their monuments were to be erected, gave the Maya ample 
time to prepare for these events, without interfering with the production of those 
food and clothes-stuffs upon which the very life of the community depended. And 
so, about the beginning of Cycle 9, the custom of erecting their monuments only on 

